Method of concentrating ores



United States 2,919,802" METHOD OF CONCENTRATING oREsv No Drawing. Application July 18, 1956 Serial No. 598,507

6 Claims. (Cl. 209-167) This invention relates to an improved method for the concentration of ores. The invention is particularly directed to improving the efiiciency of the froth flotation of ores, and particularly the concentration by froth flotation of ores which contain, in addition to desired minerals or metal values, minerals such as talc, clay, magnesia, calcium, silica and the like which, under the conditions prevailing in the preparation for and in treatment by froth flotation, convert to slimes from which it is difficult, if not impossible, to obtain a satisfactory separation of desired minerals.

The problem of the presence of slimes in the operation of conventional froth flotation processes is known and a number of addition agents have been used in an endeavour to overcome it. For. example, reagents such as dextrin and starch have been employed to arrest the tendency of the slimes to interfere with the action of the mineral collector. It is believed that the dextrin and/or starch neutralize the slime particles in such a Way that they disperse throughout the pulp and allow the collector to move between the slime particles rather than being bound in and trapped by-them.

The presence of a small amount of slimes in ore subjected to concentration by froth flotation does not present a serious problem, particularly in the preparationofore concentrates for extraction and recovery of desired minerals by conventional pyrometallurgical methods. However, the presence of appreciable amounts of slimes in the ore interferes with the efi'icient recovery of desired minerals by froth flotation, and the presence of appreciable amounts of such slimes in the ore concentrates presents a serious problem in the extraction and recovery of desired minerals, and particularly if metal values are to be extracted and recovered by hydrometallurgical processes. The difiiculty is that as the amount of slimes in the ores increases, the amount of dextrin and/or starch must be increased until the point is reached at which the addition of further amounts ofstarchor dextrin serves no useful purpose and interferes with the efiicient separation and recovery of desired minerals.

It has been found that the problem of the presence of appreciable amounts of slimes, hereinafter referred to as insoluble matter or insol, in ore subjected to'froth flotation can be overcome by the use of a combination of auxiliary agents, one of which functions as a dispersant for the slimes and the other functions in the ore pulp, as a depressant for the slimes.

The present invention is, of course, based on results obtained in exhaustive investigations conducted withfthe object of overcoming the problem attendant with the presence of appreciable amounts of. slimes in the ores and is entirely independent of hypothetical considerations. It is known that clay and talc slimes are relatively easy to fiocculate but that slimes which contain insoluble carbonates, silicates and sulphides are diflicult'to flocculate. Also, flocs of sulphide slimes, when formed, are less stable than clay flocs and are easily destroyed. A l

2,919,802. mis re t J r 1. 9

reasonable explanation of the phenomenon takes place in the operation of this invention is that the addition of a depressant for the slimes alone tends to flocculate them, entraining in .thefl oc values of minerals, par ticularly metal values, which it is desired to separateand recover from the gangue material in the pulp. Thus, while the addition of the depressant for the slimes tends to depress the slimes, it also results in the loss of desired metal values, thus lowe 'ng the overall efiiciency of thefrecovery of desired minerals' However, if a disper'sant for the slimes is added to the pii-lp' mixtur'e prior to the addition of the depressant, the slim'particlesafi dispersed in the pulp to the extent that" when the depressant is added they become inertto the action of the collector employed for the collection ofthe desiredininer als and remain suspehdedin the pulp mixture while the desired minerals riseto and overflow from the Upper part of the flotation cell. Thus, a relatively'clean separation of desired minerals can be 'olbtair'ied fromforeshwhich contain a relatively high slirfieorin'sofl content with resulting recovery of a 's'htisfac'tory concentrate in which the insol content is substantially reduced without adversely affecting the overall recovery of desired minerals.

It is found that mannogalactan possesses unusual and unexpected properties as a depressant for slimes, particularly when they are associated with an ore which contains metal values. Mannogalactan occurs in the seeds or many legumes, an example of which is the endosperm of the pod bearingflegume known as guar. Mannogalactan which occurs in guar seeds consists of approximately 67% mannose units and 33% galactose units.

However, the addition of mannogalactan alone is not sufiicient for the purpose of the present invention. It must be preceded by the'addition of a dispersant to prevent flocculation of slimes with attendant entrainment of desiredjmin i l h s, according to the present invention, a suitabledispersant is added to the pulp prior to theaddition ofthe depressant for the slimes.

'Itis found that the dispersing agent must be a relatively highly io-niz ed salt, particularly in the treatment of ores which contain a high slimes content. Alkali metal phosphates such as, sodium phosphate, sodium tripolyphosphate, sodium pyrophosphate a'nd sodium hexa: metaphospha'f'e and alkalimetal. silicates such 'as'sodium silicate. are illustrative of highly'ioriizedsalts suitable for use as dispersants in the present'invention. It is found further that the dispersing'ag'en't, in'order toobtain maxi mum effectiveness, must be added to the ore pulp or slurry prior to the addition of the collector.

In conventional flotation practice, the ore usually is subjected to a preliminary conditioning step during which the, usual collector, such as a sodium or potassium xa'n'that'efand frothing agent such as a high alcohol, are added. The conditioned ore pulp is then passed to the flotation cells. It has been found by this invention that it is very cohVeniEnFtU'aHd the dispersant for the slimes to the conditioning step, during which it is dispersed throughout the pulp mixture. The mannogalactan depressant then caiijb'ef added to the stream of pulp as it is passed from the conditioner to the flotation cells. Alternatively, of course, the various agents can be added at any other suitable point to the feed to the cells.

In the following examples which illustrate the operation of the invention, the ore subjected to the concentration process of this invention, contained pentlandite, chalcopyrite and pyrrhotite. The gangue minerals were principally talc, pyroxine and hornblende. The flotation circuit comprised a, roughencircuit. which produced a bulk nick 1 copper concentrate, 'a nickel'middling circuit final tailings were discharged and a cleaner circuit. The bulk nickel-copper concentrate was, separated in a. separation circuit into a high grade nickel concentrate and a high grade copper concentrate. Concentrate from the nickel middling cleaner circuit was added to the high grade nickel concentrate and tailings from that circuit were returned to the middling circuit.

The rougher and middling circuits were alkaline, from about pH 8 to 10, and the middling cleaner circuit was acid, about pH 6.5 with added sulphur dioxide. The ore subjected to treatment contained about 1.90% nickel, about 0.79% copper and about 65.6% insol.

The ore pulp, mixture of ore and water, about 40% by weight solids, was first conditioned for five minutes with the dispersant, about 0.4 pounds sodium hexametaphosphate per ton of ore, and the collector, potassium amyl xanthate. Aerofroth 70 was employed as a frothing agent. Mannogalactan was then added in the form of guar, about 0.3 pound per ton of ore, and the pulp was conditioned for about minute and passed to the first rougher cells. If a conditioner cell is not employed, the various agents can be added to the overflow from the classifier or to such other source of feed to the flotation circuit which may be employed.

Additional guar and dispersant were added to either or both the middling and middling cleaner circuits of the ton of ore. Greater amounts of these reagents appear to have a depressing effect on the sulphides with resultant lower metals recovery. Optimum results appear to be obtained by the use of from 0.25 to 0.35 pounds of mannogalactan and 0.35 and 0.45 pounds of dispersant per ton of ore. It is not intended that the invention should be limited to any specific amount of either or both these auxiliary reagents as these amounts must be varied with the slimes or insol content of the specific ore being treated.

In the use of the reagents employed in the operation of the present invention, the potassium amyl xanthate is a known conventional collector, the mannogalactan functions as a depressor for slimes, or insol, and also, has a selective fiocculating effect on sulphides, and the dispersant functions as a slimes dispersant and froth modifier, producing a more selective froth than is obtained by conventional practice. In addition to its functions as a slimes or insol depressant, the use of the mannogalactan has effectively reduced the amount of collector and frother oil by about one-third of that which otherwise would be required.

The improved results obtained in the operation of the present invention are illustrated in the following tables.

TABLE 1 The efiecl of using increasing amounts of guar without dispersant [Rougher circuit pH 8.6]

Assays Recoveries Tailings Guar, LbsJton of ore Percent Percent Percent Percent Percent Percent Percent Percent Ni Cu Insol. Ni Cu Insol. Ni Cu Blank, Rougher Concentrate 8. 24 4.00 40. 7 84.1 93. 3 8. 60 .27 .05 0.1# Rougher Concentrate- 8.00 3. 55 38. 2 89. 1 93. 2 8. 71 .19 .05 0.2# Rougher Concentrated 8. 24 3.60 34.8 89. 5 91. 7 7. 70 18 .05 0.3# Rougher Concentrate 9. 4. 30.0 89.0 92. 1 5. 78 18 .06 0.4# Rougher Concentrate. 9. 72 4. 55 26. 4 88. 2 90. 5 4. 83 19 .07 0.5# Rougher Concentrate 10. 20 4. 80 24.3 88. 1 90. 5 4. 20 19 .07

order of about 0.2 pounds of each reagent per ton of ore. In this, it has been found that the effectiveness of the depressant is at least partially destroyed when it is present in a pulp mixture passed through a pump. Thus, it is best to add at least this reagent to the mixture be- The use of guar alone improved the grade of concentrate by about 2%. It increased the overall recovery of metal values by about 4% and it effected a substantial reduction in the slimes or insol in the resulting concentrate.

TABLE 2 Effect of increasing amounts of guar using 0.4 lbs. sodium hexametaphosphate per ton of ore [Rougher circuit pH 9.6]

Assays Recoveries Taillngs Sodium Hexameta- Guar, Lbs/ton phosphate, Per- Per- Per- Per- Per- Per- Per- Per- Lbs./ton cent cent cent cent cent cent cent cent Ni Cu Insol. Ni Cu Insol. Ni Cu 0.20# Rougher C0ncentrate 10.37 4.08 28. 5 86.0 90. 3 8.03 .35 .09 0.25# Rougher Concentrate 10.69 4. 26 24. 7 86. 0 91.3 6. 67 .34 .08 0.30# Rougher Concentrate 11. 12 4. 45 22. 7 85.8 90.1 5. 8 .34 .09 0.35# Rougher Concentrate 11. 4. 55 19. 8 86. 2 88.2 4. 98 .34 .11 0.40# Rougher Concentrate" 11.92 4. 18. 3 85.0 89. 1 4. 48 .36 .10

tween a pump which is employed for moving it to its point of use.

The effective range of the mannogalactan appears to be of the order of from about 0.1 to about 0.5 pounds per The addition of the dispersing agent, sodium hexametaphosphate, increased the grade of the concentrate and reduced the amount of insol with only a slight de- 75 crease in the overall recovery of metal values.

TABLE 7 Efiects of increasing amounts of sodium phosphate- Na I-1PO with 0.27# guar Assays Recoveries Taflings Sodium Phosphate Gum, lbs/ton NmHPO Per- Per- Per- Per- Per- Per- Per- Per- Lbs./ton cent cent cent cent cent cent cent cent Ni Cu Insol. Ni Cu Insol. Ni Cu 0.18;. 0.273 Rongher Concentrate" 9. 4. 32 31. 2 87.5 89.1 6. 43 22 .09 0.27;? .do 10. 12 4. 67 28. 8 86. 7 87. 8 5. 46 24 10 6? 8.84 4.22 28 3 88.0 90. 2 6.00 .21 .08

Hexametephosphate, lbs/ton:

0.362 0.279 Standard Concentrate. 9.28 4.37 30 3 88 8 89 2 6 25 .20 .09

TABLE 8 Efiects of increasing amounts of tripolyphospkate- Na P O with 0.264%: guar Sodium Assays Recoveries Tailings Tripoly- Phosphate Guar, 1bs./ton N 21 F 01), Per- Per- Per- Per- Per- Per- Pen Per- Lbs./ton cent cent cent cent cent cent cent cent Ni Cu Insol. Ni Cu Insol. Ni Cu 0.17# 0.269 Rougher Concentrate.. 7.92 3.62 28.8 88.7 93.0 7.63 .22 .06 7. 76 3. 55 28. 3 88. 6 91. 8 7. 58 22 .07 8. 32 3. 90 26. 7 87. 6 93. 0 6. 70 24 08 8.72 4.08 23.7 87.9 90.3 5.4 .22 .08

Hexameta- Phosphate, lbs/ton:

0.34# 0.260 Standard Concentrate. 8.56 3.97 27.6 87.8 88 3 6.48 .23 .10

TABLE 9 Efiects of increasing amounts of pyrophosphate Na P 0 with 0.31? guar Assays Recoveries Tailings Pyrophosphate Guar, lbs/ton N84PQO7, Per- Per- Pcr- Per- Per- Per- Per- Per- LbsJton cent cent cent cent cent cent cent cent Ni Cu Insol. Ni Cu lnsol. Ni 11 0.2%. 0.32 Rougher Concentrate... 9 96 4.40 25.0 85.2 92. 5 5.36 .06 0.3%. d0 9 24 3.92 23.2 88.6 92.7 6.66 .23 .06 0.459 8. 56 3. 72 22. 6 38. 0 91. 6 5. 90 24 07 0.51; 9. 96 4. 30 18.8 87.7 91. 3 4. 14 24 Sodium Hexemeta- Phosphate. lbsJton:

0.4% 0.3;? Standard Concentrate- 9.00 3.85 25.3 87 9 90 3 6. 11 .24 .08

TABLE Efiects of increasing amounts of sodium silicate with 0.3# guar Assays Recoveries Taflmgs Sodium Silicate, Guer, lbs/ton LbsJton Per- Per- Per- Per- Per- Per- Per- Percent cent cent cent cent cent cent cent N1 Cu Insol. Ni Cu Insol. Ni Cu 0.53 0.3{1Rougher Concentrate-.. 10. 16 4. 57 24. 1 88 2 89.8 4 71 .21 .08 1.0# do 11. 46 5. 20.1 87 4 90. 7 3 41 22 07 1.53-. 10.92 4.95 20.7 87 5 90.9 3 72 .22 .07 2.0# 12. 5. 17. 2 86 0 89. 4 2 69 24 08 2.5;? 12.32 5.65 16.4 86 6 89.6 2 61 .23 Sodium Hexameta- Phosphate. lbs/ton;

The process of the present invention processes a number of important advantages. Primarily, the slimes or insol content of an ore which contains a high slimes con-v tent is substantially reduced to the extent that a satisfactory ore concentrate can be produced with which no particular difliculties are encountered during its subsequent treatment, whetherby pyrometallurgical or hydrometallurgical methods for the extraction and recovery of desired metal values. The use of the auxiliary reagents does not add appreciably to the overall cost per ton of preparing the ore concentrate. Also, of course, the reagents can be added easily to the pulp mixture and their presence does not create new problems either in the froth flotation process or in subsequent treatment processes to which the ore concentrate is subjected.

It will be understood, of course, that modifications can be made in the operation of the process of the present invention Without departing from the scope of the invention as defined by the appended claims.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. In a method of separating valuable constituents from metal bearing sulphide ores which contain slime forming constituents, the improvement which comprises subjecting a metal bearing sulphide ore pulp to froth flotation in the presence of a mineral collector, a finite amount of mannogalactan as a depressant for slimes and a finite amount of a compound selected from the group consisting of alkali metal phosphates and alkali metal silicates as a dispersant for said slimes, said dispersant having been added to the ore pulp prior to the addition of the mannogalactan.

2. In a method of separating valuable constituents from metal bearing sulphide ores which contain slime forming constituents, the improvement which comprises subjecting a metal bearing sulphide-ore pulp to froth flotation in the presence of a mineral collector, a finite amount of mannogalactan as a depressant for slimes, and a finite amount of a dispersant for slimes of the group consisting of alkali metal phosphates, alkali metal pyrophosphates, alkali metal polyphosphates, and sodium silicate, the dispersant having been added to the ore pulp nrior to the addition of the mannogalactan.

3. In a method of separating valuable constituents from 10 metal bearing sulphide ores which contain slime forming constituents, the improvement which comprises subjecting a metal bearing sulphide ore pulp to froth flotation in the presence of a mineral collector, from about 0.1 to 0.5 pound of mannogalactan as a depressant for slimes per ton of ore and from about 0.2 to 0.5 pound per ton of ore of a dispersant for slimes of the group consisting of alkali metal phosphates, alkali metal pyrophosphates, alkali metal polyphosphates, and sodium silicate, the dispersant having been added to the ore pulp.

prior to the addition of the mannogalactan.

4. In a method of separating valuable constituents from metal bearing sulphide ores, the improvement which comprises subjecting a metal bearing sulphide ore pulp to froth flotation in the presence of a mineral collector, from about 0.1 to about 0.5 pound of guar per ton of ore and from about 0.2 to about 0.5 pound per ton of ore of a compound selected from the group consisting of alkali metal phosphates and alkali metal silicates, the said compound having been added to the ore pulp prior to the addition of the guar.

5. The method according to claim 4 in which the said compound is a member selected from the group consisting of alkali metal pyrophosphates and alkali metal polyphosphates.

6. In a method of separating valuable constituents from metal bearing sulphide ores, the improvement which comprises subjecting a metal bearing sulphide ore pulp to froth flotation in the presence of a mineral collector, from about 0.1 to 05 pound of guar per ton of ore and from about 0.2 to 0.5 pounds of sodium silicate per ton of ore, the sodium silicate having been added to the ore pulp prior to the addition of guar.

References Cited in the file of this patent UNITED STATES PATENTS 1,454,838 Borcherdt May 8, 1923 2,696,912 Atwood Dec. 14, 1954 2,724,499 Smith Nov. 22, 1955 2,740,522 Aimone Apr. 3, 1956 OTHER REFERENCES Taggart: Handbook of Mineral Dressing, 1945, p. 12-21, 12-108. 

1. IN A METHOD OF SEPARATING VALUABLE CONSTITUENTS FROM METAL BEARING SULPHIDE ORES WHICH CONTAIN SLIME FORMING CONSTITUENTS, THE IMPROVEMENT WHICH COMPRISES SUBJECTING A METAL BEARING SULPHIDE ORE PULP TO FROTH FLOTATION IN THE PRESENCE OF A MINERAL COLLECTOR, A FINITE AMOUNT OF MANNOGALACTAN AS A DEPRESSANT FOR SLIMES AND A FINITE AMOUNT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL PHOSPHATES AND ALKALI METAL SILICATES AS A DISPERSANT FOR SAID SLIMES, SAID DISPERSANT HAVING BEEN ADDED TO THE ORE PULP PRIOR TO THE ADDITION OF THE MANNOGALACTAN. 